The present invention relates to computer systems, and in particular to computer systems having processing units, which are connectable to a communications network via which data may be communicated.
There are many fields in which mankind has become reliant on computers to perform valuable and sometimes essential functions. The reliance on computer systems demands that the down time of a computer system is as small as possible. The down time of a computer system is a period during which a computer system is inoperable as a result of a fault in the system. If a computer system goes down, the inconvenience and loss of revenue caused can be substantial. For example, if a computer system is operating as a server or exchange forming part of a telecommunications system, then during the down time no communications can be performed using the telecommunications system, which can result in a considerable loss of business and therefore revenue for an organization. Computer systems are therefore arranged to be as reliable as possible, so that the down-time is reduced to a minimum. Accordingly, the up-time of a computer system is required to be in the order of 99.9995%, which equates approximately to a down-time of a few seconds per year.
Computer systems are designed and manufactured to standards which reduce as far as possible the likelihood of malfunction. However, in order to minimize any down-time, which may occur as a result of a malfunction, it has been proposed to design parts of the computer system such that the parts can be replaced as quickly as possible with a part which performs the same function. For example, a processing unit, which includes for example a hard-disc drive, can be arranged to be replaceable. The processing unit often forms part of a computer system which executes software processes which control the computer system. As such, when a malfunction occurs in the processing unit, the unit is replaced by an equivalent processing unit. To this end, the hard-disc of the unit is often provided with pre-loaded software which is equivalent to the software processes loaded onto the original hard-disc. The original processing unit may then be repaired off-line, which is particularly advantageous because the repairs can be time consuming.
Computer systems often include, or are arranged to be connectable to a communications network. This can be used to effect communications between different parts of the computer system, the communications network being a local bus, or communications between different computer systems, the communications network being a local area network or the like.
In order to effect replacement of a processing unit, the replacement processing unit should be arranged to communicate via the communications network, in substantially the same way as the original processing unit communicated. In order to minimize down time, it is desirable that the replacement is made as quickly and efficiently as possible.